Melanin concentrating hormone (hereafter abbreviated as “MCH”) is a cyclic peptide hormone/neuro-peptide, which was for the first time isolated by Kawauchi, et al. in 1983 from sermon hypophysis [Nature, Vol. 305, 321 (1983)]. The hormone is known to functionally antagonize to melanin cell stimulating hormone in fishes, to cause concentration of melanin granules in melanophore and participate in body color change [International Review of Cytology, Vol. 126, 1(1991); Trends in Endocrinology and Metabolism, Vol. 5, 120 (1994)]. Also in mammals, MCH-containing neuron nerve cells are localized in the hypothalamus lateral field and uncertain zone, but their nerve fibers are projecting over a very wide scope in the brain [The Journal of Comparative Neurology, Vol. 319, 218 (1992)], and MCH is considered to preside over various central functions in living bodies.
Hypothalamus lateral field is known of old as feeding center, and furthermore, recently molecular biological and pharmacological knowledges suggesting participation of MCH in controlling energetic homeostasis are being accumulated. That is, it has been reported that expression of mRNA, which is a MCH precursor, was accelerated in brains of ob/ob mouse, db/db mouse, Ay/a mouse, Zucker fatty rat or the like which are model animals of hereditary obesity, or in brains of fasted mice [Nature, Vol. 380, 243 (1996); Diabetes, Vol. 47, 294 (1998); Biochemical and Biophysical Research Communications, Vol. 268, 88 (2000); Molecular Brain Research, Vol. 92, 43 (2001)].
Acute ventricular administration of MCH to rats was observed to induce accelerated feeding activity [Nature, Vol. 380, 243 (1996)] and chronic administration invites obesity accompanied by polyphagy [Proceedings of the National Academy of Science of the United States of America, Vol. 99, 3240, (2002)]. Moreover, MCH precursor gene-deficient mouse shows reduced food ingestion or rise in oxygen consumption per body weight compared to wild type mice. Its low body weight due to decrease in body fat was observed [Nature, Vol. 396, 670 (1998)].
On the contrary, transgenic mouse which expresses excessive MCH precursor develops obesity accompanied by polyphagy and insulin resistance [The Journal of Clinical Investigation, Vol. 107, 379 (2001)]. Consequently, it is suggested that MCH is an important factor for developing obesity and participates in diseases induced by metabolic disorder or respiratory diseases of which one of risk factors is obesity. Besides, MCH is known to participate also in anxiety-causing action, epilepsy, memory, learning, diuretic action, excretory action of sodium and potassium, oxytocin secreting action, reproduction and reproductive function [Peptides, Vol. 17, 171 (1996); Peptides, Vol. 18, 1095 (1997), Peptides, Vol. 15, 757 (1994); Journal of Neuroendocrinology, Vol. 8, 57 (1996); Critical Reviews in Neurobiology, Vol. 8, 221, (1994)].
MCH causes versatile pharmacological actions through MCH receptors which are present mainly in the central nervous system. As receptors of MCH, at least two types of type 1 receptors (MCH-1R or SLC-1) and type 2 receptors (MCH-2R or SLT) are known [Nature, Vol. 400, 261 (1999); Nature, Vol. 400, 265 (1999); Biochemical and Biophysical Research Communications, Vol. 261, 622 (1999); Nature Cell Biology, Vol. 1, 267 (1999); FEBS Letters, Vol. 457, 522 (1999); Biochemical and Physical Research Communications, Vol. 283, 1013 (2001); The Journal of Biological Chemistry, Vol. 276, 20125 (2001); Proceedings of the National Academy of Sciences of the United States of America, Vol. 98, 7564 (2001); Proceedings of the National Academy of Sciences of the United States of America, Vol. 98, 7576 (2001); The Journal of Biological Chemistry, Vol. 276, 34664 (2001); and Molecular Pharmacology, Vol. 60, 632 (2001)].
Of those, the pharmacological action observed on rodents is induced mainly via MCH-1R [Genomics, Vol. 79, 785(2002)]. Because MCH-1R gene-deficient mice chronically administered with MCH do not develop polyphagy or obesity, it is known that controlling of energy exchange by MCH is induced via MCH-1R. Furthermore, deficiency of MCH-1R promotes activity amount of mouse [Proceedings of the National Academy of Sciences of the United States of America, Vol. 99, 3240 (2002)], and its participation in central diseases accompanied by behavioral disorder, for example, attention-deficit hyperactivity disorder, schizophrenia and the like also is strongly suggested [Molecular Medicine Today, Vol. 6, 43 (2000); Trends in Neuroscience, Vol. 24, 527 (2001)].
It is also reported that autoantibody to MCH-1R is present in serum of vitiligo vulgaris patient [The Journal of Clinical Investigation, Vol. 109, 923 (2002)]. Furthermore, expression of MCH-1R in certain species of cancer cells was reported, and in vivo expression sites of MCH and MCH-1R also suggest their participation in cancer, sleep, vigil, drug dependence and digestive disorders [Biochemical and Biophysical Research Communications, Vol. 289, 44 (2001); Neuroendocrinology, Vol. 61, 348 (1995); Endocrinology, Vol. 137, 561 (1996); The Journal of Comparative Neurology, Vol. 435, 26 (2001)].
Functions of MCH are expressed upon its binding to MCH receptors. Therefore, when its binding to MCH receptor is inhibited, expression of MCH action can be inhibited. In consequence, substances which are antagonists to binding of MCH to its receptor are useful as preventing or treating agent of those various diseases in which MCH participates, for example, metabolic disorders represented by obesity, diabetes, hormone disorder, hyperlipidemia, gout, fatty liver, hepatitis and cirrhosis; cardiovascular disorders, represented by stenocardia, acute or congestive heart failure, myocardial infarction, coronary atherosclerosis, hypertension, renal diseases and electrolyte abnormality; central nervous system or peripheral nervous system disorders represented by bulimia, emotional disturbance, depression, anxiety, epilepsy, delirium, dementia, schizophrenia, attention-deficit hyperactivity disorder, memory impairment, sleep disorders, cognitive failure, dyskinesia, paresthesias, smell disorders, morphine tolerance, drug dependence and alcoholism; reproductive disorders represented by infertility, preterm labor and sexual dysfunction; digestive disorders; respiratory disorders; cancer or pigmentation.
As compounds analogous to the compounds of the present invention, for example, JP Tokuhyo (public announcement) Hei 10(1998)-500960A shows the following:

These compounds exhibit 5HT1D-antagonistic activity and include indole skeleton, indoline skeleton and the like but do not include imidazopyridine skeleton, and are different from the compounds of the present invention in mechanism of the action and utility.
On the other hand, as known antagonist to melanin concentrating hormone receptor, there are those described in, for example, International Publications WO 01/21577 Pamphlet and WO 01/82925 Pamphlet. In particular, WO 01/82925 shows the following compounds as melanin concentrating hormone receptor antagonist:

This reference does neither refer to imidazopyridine ring as Ar nor contain any specific disclosure on compounds having specific substituents at specific sites of imidazopyridine ring or on production process of such compounds. Hence no person skilled in the art who read WO 01/82925 Pamphlet could easily anticipate that the imidazopyridine derivatives of the present invention exhibit excellent action as melanin concentrating hormone receptor antagonist.
Patent literature 1: WO 01/21577
Patent literature 2: WO 01/82925
This invention aims at provision of piperidine derivatives having the action to inhibit binding of MCH to MCH-1R and also to provide preventing or treating agents for cardiovascular disorders, nervous disorders, metabolic disorders, reproductive disorders, respiratory disorders, digestive disorders and the like.